You don’t need his permission to get the passport but you’ll need written permission to take them away on holiday as they do often check at the airports and if they have different last names to yourself then you’ll have to carry a birth certificate through the airport x
My little boy is in his dad’s last name. Didn’t even question me at the airport. On the way back got asked if he was nine & I said well yeah & that was it. His dad didn’t give me permission but I still went x
U don’t need his permission,